A depth of field of a photographed image obtained by a medical microscope or the like is shallow, where an image of an object at a slightly different depth from a focus position (focus plane) that is in focus in a real space is blurred.
In a photographed image obtained by the medical microscope in a brain surgery, for example, a frontward object is photographed in the periphery while an object (such as a surgical site) being a focus of attention located more or less at the back is photographed at the center. At this time, the object in the periphery of the photographed image is blurred when a focus is adjusted to bring the object at the center of the photographed image into focus, which may affect observability of the object and operability of the medical microscope.
Accordingly, for example, there is proposed a real-time all-in-focus microscopic camera which performs high-speed photographing of an image while changing a focus position (focal length) and obtains a deep focus image (an all-in-focus image) from a plurality of images obtained by the photographing (refer to Patent Literature 1, for example).